1. Field of the Invention
The present invention relates to a card processing system, for example, for payment of tolls of toll roads by a prepaid-type IC card, and an antenna unit used for this system.
2. Description of the Related Art
Currently, magnetic-type prepaid cards (hereinafter, referred to as magnetic cards) that are widely available in the market are highly convenient for users in that they can be used anonymously for an indefinite term by an unspecified number of persons. On the other hand, the magnetic cards are always accompanied by a risk of unauthorized rewriting of data such as amount information and has a security weakness, so that the operation of magnetic cards are generally performed in such a manner that the subtraction of balance amount is only performed in the use of magnetic cards, and they are disposed of when their balance amount becomes zero.
Thus, in recent years, for the purpose of increasing security, such a highly convenient magnetic card as described above is replaced by an IC card. For example, as described in Japanese Patent No. 3256642, in public transport such as railroads, there is already realized a card processing system using a wireless-type prepaid IC card that allows entrance and exit by bringing it into contact with or presenting it above an automatic ticket checker installed at a ticket gate of a railroad station or the like. A wireless system is disclosed, for example, in U.S. Pat. No. 4,243,980 and U.S. Pat. No. 4,866,455.
This wireless-type prepaid IC card (hereinafter, referred to as an IC card) is considered to be introduced to a toll collection on toll roads. In this application of the IC card to the toll collection on toll roads, an operation is assumed that a person holds out the IC card to inside of a distance which allows communication with an antenna while the person is staying in a vehicle.
Generally, on the automatic ticket checker, when either surface of the IC card is positioned to face an antenna surface, magnetic flux in a direction perpendicular to these surfaces passes through respective coils of both the antenna and card, and an induced voltage generated by induced magnetic flux of these two coils are used to realize power transmission and wireless communication. Incidentally, the communication distance of the IC card of an electromagnetic induction type is 100 mm or less.
However, there is expected a situation to occur that, when a vehicle is stopped at a position away from the antenna, the IC card held out from a window of the vehicle cannot reach inside the communication distance with the antenna. In addition, regarding the introduction of the IC card to toll roads, since there exists a construction gage (250 mm for expressways for example) as a contacting clearance between a vehicle and a building, holding out the IC card to reach inside the communication distance with the antenna is possible but may be difficult for a driver of the vehicle, even with a pulling over of the vehicle to a roadside device being taken into consideration.
It is an object of the present invention to provide an antenna unit and a card processing system which allow a user to present an IC card inside a communication distance of an antenna of a roadside device without any difficulty.
Further, it is an object of the present invention to provide an antenna unit and a card processing system which are capable of increasing reliability of communication between an IC card and an antenna.